全新java初学者实践教程6(Java SE5.0版)
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h' 基本语法3
ujq=F ZC`wO%, KNpl:g3{<Q 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
+LZLy9iKt i&66Fi1 [font="Times] 1.循环语句[font="Times]:while,do-while,for
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[font="Times]2.分支语句[font="Times]:if-else,switch,
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DvJ 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
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#9}D4i.`} 4.异常处理语句[font="Times]:try-catch-finally,throw
u#;7<.D (%e.:W${ 实践:
T?soJ]A [font="Times] 1.循环语句
?2;&O`x* [font="Times] while 语句
ag#S6E^%S [font="Times]class While {
z.9U}F [font="Times]public static void main(String args[]) {
mD0f<gJ1 [font="Times]int n = 10;
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[font="Times]while(n > 0) {
M!A}NWF [font="Times]System.out.println("tick " + n);
A8fOQ [font="Times]n--;
;F!5%}OcL% [font="Times]}
iWB=sL&p [font="Times]}
aS{n8P6vW [font="Times]}
z/WE,R [font="Times] do…while 语句
[.'|_l [font="Times] class DoWhile {
<+Dn8 [font="Times]public static void main(String args[]) {
3<Zq ]jk?n [font="Times]int n = 10;
bv9i*] [font="Times]do {
gG:Vt}N [font="Times]System.out.println("tick " + n);
EQyC1j [font="Times]n--;
LX7FaW [font="Times]} while(n > 0);
T/Gz94c [font="Times]}
B^Nf #XN( [font="Times]}
;R5`"` 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
%C'?@,7C [font="Times] for语句
&Gn 2tr [font="Times] class ForTick {
W5lR0)~#* [font="Times]public static void main(String args[]) {
H*QIB_ [font="Times]int n;
#!qm ZN [font="Times]for(n=10; n>0; n--)
c~$)UND^ [font="Times]System.out.println("tick " + n);
Y1OkkcPb{ [font="Times]}
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KL:j?.0 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
X_ cV%# 还有啊,[font="Times]for循环的部分可以为空的
{M$1N5Eh [font="Times]class ForVar {
3yY}04[9< [font="Times]public static void main(String args[]) {
(GuzN [font="Times]int i;
>#;.n(y [font="Times]boolean done = false;
+0%w ;'9z [font="Times]i = 0;
HU}7zK2 [font="Times]for( ; !done; ) {
_ Yx]_Y9I [font="Times]System.out.println("i is " + i);
YTX,cj#D^& [font="Times]if(i == 10) done = true;
i]y<|W)Q3 [font="Times]i++;
:O?MSS;~ [font="Times]}
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循环语句的例子下载 axRV:w;E< [font="Times] 2.分支语句[font="Times]
[b<oDX# [font="Times] if/else语句
|zNX=mAV [font="Times]class IfElse {
_AYK435>N [font="Times]public static void main(String args[]) {
o\<ULW* [font="Times]int month = 4; // April
*@r/5pM2} [font="Times]String season;
69?wc! [font="Times]if(month == 12 || month == 1 || month == 2)
Un(aW=PQ0 [font="Times]season = "Winter";
M~#g RAUJ [font="Times]else if(month == 3 || month == 4 || month == 5)
Xe'x[(l [font="Times]season = "Spring";
bv9]\qC]T< [font="Times]else if(month == 6 || month == 7 || month == 8)
p2[n$61 [font="Times]season = "Summer";
_476pZ_ [font="Times]else if(month == 9 || month == 10 || month == 11)
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S [font="Times]season = "Autumn";
>~sI8czR* [font="Times]else
-M~:lK]n [font="Times]season = "Bogus Month";
dulI&_x [font="Times]System.out.println("April is in the " + season + ".");
GR.^glG?6 [font="Times]}
u+e{Mim [font="Times]}
Z{Qu<vy_ [font="Times]//这段程序输出[font="Times]:
Y3cMC) [font="Times]//April is in the Spring.
hh)`645=x [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
B6nX$T4zP [font="Times] switch语句
'!cCMTj [font="Times] class Switch {
TnOggpQ6X [font="Times]public static void main(String args[]) {
qIE9$7*X [font="Times]int month = 4;
[nG<[<0G; [font="Times]String season;
<8i//HOE [font="Times]switch (month) {
'8.r-`l( [font="Times]case 12:
B+VubUPMS [font="Times]case 1:
<X^@*79m [font="Times]case 2:
eIEeb,#i [font="Times]season = "Winter";
q&-`,8# [font="Times]break;
|`,2ri*5A [font="Times]case 3:
|=ba9&q [font="Times]case 4:
ufZDF=$7 [font="Times]case 5:
7P5)Z-K[ [font="Times]season = "Spring";
Rz:]\jcIT/ [font="Times]break;
F>6|3bOR [font="Times]case 6:
b:m88AG [font="Times]case 7:
gNrjo= [font="Times]case 8:
UiP"Ixg6 [font="Times]season = "Summer";
6|%?te x [font="Times]break;
\?ZB]*Fu [font="Times]case 9:
T|op$ s| [font="Times]case 10:
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]; [font="Times]case 11:
Y%aCMP9j~9 [font="Times]season = "Autumn";
!r8`Yr n [font="Times]break;
YQ)kRhFA [font="Times]default:
c(m<h+2VL [font="Times]season = "Bogus Month";
1 ~*7f> [font="Times]}
]BZA:dd.G [font="Times]System.out.println("April is in the " + season + ".");
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分支语句代码下载 y0.'?6k z}9(x.I [font="Times]switch语句适合于条件非常多的逻辑
w"|L:8 请看上述语句可以混合使用,请看
下载例子